For his brackets, if there is a tie atop a conference, he uses the highest RPI team as the auto-bid.  53rd overall on the S-curve would equate to about a 13 seed. 

13 Seeds = 51-54
14 seeds = 55-58
15 seeds = 59-62
16 seeds = 63-68

Do not count on an at-large bid.

I was with the team at the OU Inn on Selection Sunday in '95 when the Bobcats were left out after big OOC wins, pre-season NIT championship and #14 ranking. I never want to go through that sports drama and heartbreak again.

Well usually about the top 50 or so in the committee's eyes get in to the tournament though we never know exactly where the committee would rank the first bubble team out with respect to the last 16 or so automatic qualifiers but you can usually tell that its around 50 or 51.  That's the real goal for a bubble team - to get into the top 50 and not the top 68 best teams as you sometimes hear in February.  Many of the Automatic qualifiers with worse resumes that the best bubble team out would still be in the top 68 even though they aren't in the top 50.  Usually, though, the worst team in the tournament is a .500 team that was the 5th seed in one of the very weakest conferences and has a RPI (and any other system that you might imagine) pushing 200 or even greater.  But yeah, being the 53rd best team in the country would land a 13.  Being #63 might get a 14.  If it didn't it would get a 15.  Even if all of the #1 seeds won their tournaments it still #63 would never result in a 16 because there are about 8 to 10 conferences where even a team that is both the conference champion and then wins the conference tournament is still usually not a top 68 resume.